Food and drink safety is one of the most urgent needs in our daily life, and recently, food and drink safety has attracted great public attention, especially since the occurrence of Escherchia coli O157:H7 in beef, the occurrence of the dioxin egg scandal and recent scandals of melamine in infant formula and plasticizers in food and drinks.
Phthalate is known as an endocrine disrupter which produces reproductive and developmental toxicity, which may cause miscarriage, fewer motile sperm and external sex organs malformation of infant. Melamine, known as a triazine heterocyclic organic chemical material, can block and damage renal cells, resulting in kidney malfunction, and even death in infants. Such foodborne hazards come either from environmental hazards, e.g. contamination of phthalate plasticizers from processing equipment such as piping or container, or from illegal addition driven by economic benefit, e.g. melamine in infant formula and plasticizer contaminations in food and drinks in recent times. Public attention to food scandals raises an urgent need for detecting food contaminants and has imposed a pressing demand for rapid, inexpensive but effective and reliable methods to detect the food contaminations.
However, the current available techniques or prevailing detections are primarily based on liquid chromatography (e.g. high performance liquid chromatography (HPLC)), mass spectroscopy (MS) or colorimetric methods, which are restricted by sophisticated and time-consuming steps, inadequate detection limits and sample preparation which may include complicated sample pretreatment steps such as extraction, preconcentration, and derivatization.
Surface enhanced Raman scattering (SERS) spectroscopy may also be used for detection purposes. SERS spectroscopy is an extremely sensitive analytical technology used to detect and identify molecules, and is capable of providing highly resolved specific vibrational molecular information, and requires little sample preparation. The essential idea towards high sensitivity SERS detection is the engineering of noble metal containing substrates for achieving a highly localized electromagnetic field, which leads to a very strong electromagnetic enhancement. It has been shown that an enhancement factor (EF) value between 1×106 and 1×108 is adequate to achieve single molecule detection. In the past decades, many developments have been achieved on SERS-active nanostructures, such as gold (Au) and silver (Ag) nanoparticles, nanoshell, and colloidal metal nanoparticles arrays. However, many SERS-active substrates suffer from poor reproducibility of “hot spots”, which refer to regions of enhanced electric field. It is thus a major challenge to reproducibly prepare stable SERS substrates with uniform “hot-spots” and controllably push the interior gap between nanostructures to sub-nm regime.
There is therefore need for a detection strategy that exhibits high sensitivity and specificity, requires a minimal sample preparation with rapid detection and low-cost.